1. Field of the Invention
This invention relates generally to a method and structure for repairing or making engineering changes to circuit boards having land grid array pads or other electrical interfaces; and, more particularly, to a method and repair structure for replacing individual pads and vias or plated through holes in land grid array or other electrical interface circuit boards having a large number of contact pads and vias.
2. Background Information
Many circuit boards with land grid arrays (LGAs) or other electrical interfaces have a very large number of connections and vias or plated through holes extending from the external connections on one surface of the board to internal wiring, and to wiring and connections on the opposite surface. Indeed, with the present technology, there are up to as many as 41,000 connections, many with associated vias or plated through holes, and this number is increasing as technology advances. In many instances, if a few or even one of these connections is defective, the entire board is defective and the connection and associated via must either be repaired or replaced or the entire board scrapped. Also, the circuit board with an LGA is typically used with an interposer which mounts a module thereon, which module has an integrated circuit chip mounted thereon. Any repair must be transparent to the module and accommodate such a mounting structure. Also, circuit boards having LGAs typically have internal circuitry and the repair must isolate this internal circuitry and provide additional connections to the internal circuitry through topside or bottom side metallurgy.